Network security is a weak link in wired and wireless network systems. Malicious attacks have caused tremendous loss by impairing the functionalities of the computer
networks.Denial of Service (DoS) and Distributed DoS (DDoS) attacks are two of the most harmful threats to the network functionality. Mobile Ad Hoc Networks (MANET) are even more vulnerable to such
attacks.. Denial of Service (DoS) is the degradation or prevention of legitimate use of network resources. The wireless ad hoc network is particularly vulnerable to DoS attacks due to its features
of open medium, dynamic changing topology,cooperative algorithms,decentralization of the protocols, and lack of a clear line of defense is a growing problem in networks today. Many of the defense
techniques developed on a fixed wired network are not applicable to this new mobile environment. How to thwart the DoS attacks differently and effectively and keep the vital security-sensitive ad hoc networks available for its intended use is essential.